Citrus cultivars and relatives, even within the
same group, tend to exhibit variable reactions to CTV
infection. Limes, grapefruit, and Alemow
(
Citrus
macrophylla
) are highly susceptible to CTV-SP.
Sweet oranges and rough lemon are tolerant to many
CTV isolates, but show strong stem pitting when
infected by CTV-SP. Mandarins are considered
tolerant, but may show stem pitting under some
conditions. Trifoliate orange and trifoliate hybrids
carrying the CTV-resistance gene are resistant to
CTV infection and CTV-SP, but hybrids without this
gene may show strong pitting. Some pummelos show
selective resistance specific to some severe CTV-SP
isolates, but are highly susceptible to others. It
appears that several independent virus factors cause
stem pitting in different hosts.
Tristeza
-induced stem
pitting and decline are also apparently under separate
genetic control. Decline isolates often do not cause
stem pitting and some CTV-SP isolates do not cause
decline or seedling yellows (another symptom
associated with decline isolates of CTV).
Citrus cultivars and relatives, even within the same group, tend to exhibit variable reactions to CTV infection. Limes, grapefruit, and Alemow(Citrus macrophylla) are highly susceptible to CTV-SP. Sweet oranges and rough lemon are tolerant to many CTV isolates, but show strong stem pitting when infected by CTV-SP. Mandarins are considered tolerant, but may show stem pitting under some conditions. Trifoliate orange and trifoliate hybrids carrying the CTV-resistance gene are resistant to CTV infection and CTV-SP, but hybrids without this gene may show strong pitting. Some pummelos show selective resistance specific to some severe CTV-SP isolates, but are highly susceptible to others. It appears that several independent virus factors cause stem pitting in different hosts. Tristeza-induced stem pitting and decline are also apparently under separate genetic control. Decline isolates often do not cause stem pitting and some CTV-SP isolates do not cause decline or seedling yellows (another symptom associated with decline isolates of CTV).
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